Article
Chemistry, Physical
Mao Ye, Kenta Kuroda, Mikhail M. Otrokov, Anastasia G. Ryabishchenkova, Qi Jiang, Arthur Ernst, Evgueni Chulkov, Masashi Nakatake, Masashi Arita, Taichi Okuda, Tomohiro Matsushita, Laszlo Toth, Hiroshi Daimon, Kenya Shimada, Yoshifumi Ueda, Akio Kimura
Summary: The study reveals that deposited Ag atoms on the topological insulator Bi2Se3 surface are stabilized beneath the surface instead of being adsorbed on the topmost surface. The presence of Ag atoms does not disturb the topological surface states. Through angle-resolved photoemission spectroscopy and first-principles calculations, the distribution and most favorable locations of Ag atoms beneath the surface are identified.
JOURNAL OF PHYSICAL CHEMISTRY C
(2021)
Article
Chemistry, Physical
J. D. Fuhr, J. E. Gayone, H. Ascolani
Summary: The growth of Sn deposited on the Ag(111) surface at low temperatures was studied using a combination of LEED, STM experiments, and DFT calculations. Two phases were observed: a (4 x 4) phase and a (root 7 x root 7)R19 degrees phase. High-resolution STM images showed nearly planar islands and a characteristic of Sn layer is the coexistence of Sn atoms with three and four neighbors.
JOURNAL OF PHYSICAL CHEMISTRY C
(2021)
Article
Materials Science, Multidisciplinary
Jiacheng Gao, Zhaopeng Guo, Hongming Weng, Zhijun Wang
Summary: The study of magnetic topological materials is of great interest for realizing novel topological phases and pursuing potential applications in low-energy consumption spintronics. In this research, starting from the theory of nonmagnetic topological quantum chemistry, the researchers obtained irreducible (co)representations and compatibility relations in momentum space and constructed a complete list of magnetic band (co)representations in real space. They also developed symmetry indicators (SIs) to diagnose topological magnetic materials and identified numerous magnetic topological candidates through spin-polarized calculations.
Article
Crystallography
Mustahseen M. Indaleeb, Sourav Banerjee
Summary: The article investigates the phenomenon of Dual-Dirac-like cones (DDC) occurring simultaneously at the center of the Brillouin zone and how to achieve this phenomenon through tuning parameters. Results show that the antisymmetric deaf bands at different energy levels play a crucial role in tracking the DDC. By rotating the PnCs mechanism, frequencies are successfully tracked to form the DDC.
Review
Nanoscience & Nanotechnology
S. Colonna, R. Flammini, F. Ronci
Summary: This paper reviews the research activity of the author's group in the field of silicene synthesis and properties, focusing on the interaction between silicon deposition and silicon substrate, and discussing the debated formation of silicene from unsaturated silicon compounds.
Article
Materials Science, Multidisciplinary
Alexander Khaetskii, Vitaly Golovach, Arnold Kiefer
Summary: In this study, we revisit the problem of surface states in semiconductors with inverted-band structures and clarify the confusion regarding their origin, topological nature, and the role of strain. With a minimalistic description, we reconcile different solutions found in the 1980s with modern-day numerical simulations, allowing us to accurately identify all branches of surface states in different regions of the Brillouin zone.
Article
Chemistry, Physical
Xianghui Duan, Baozeng Zhou, Xiaocha Wang
Summary: This paper proposes a dumbbell-like CxNy structure and analyzes the effects of different substitutional doping of C atoms. DB-C9N exhibits metallic behavior, while DB-C4N-1 and DB-C4N-2 have a gap-opening Dirac electronic state under the influence of spin-orbit coupling, and DB-C4N-3 is an indirect band-gap semiconductor. Among them, only DB-C7N2 and DB-C7N3 are magnetic, but DB-C7N2 behaves as a metal and DB-C7N3 is a bipolar magnetic semiconductor. DB-C6N4 is a nonmagnetic semiconductor with a direct band gap.
APPLIED SURFACE SCIENCE
(2023)
Article
Chemistry, Physical
Prineha Narang, Christina A. C. Garcia, Claudia Felser
Summary: The study of topology in relation to physical systems has rapidly advanced in the past decade, with a focus on understanding materials exhibiting new topological phases and precise control of material chemistry. New theoretical methods and the synthesis of high-quality single crystals play a key role in identifying topological material candidates, warranting discussion at an accessible level. This Perspective provides a broad introduction to topological materials science, with a particular emphasis on semimetals such as topological Weyl and Dirac semimetals.
Article
Materials Science, Multidisciplinary
Chiranjit Mondal, Sunje Kim, Bohm -Jung Yang
Summary: The article introduces a new concept of topological semimetals - linking structure, discusses the formation of linked nodal structure under specific symmetry conditions, and proposes a potential material system. The linked nodal structure, with additional chiral and rotational symmetries, is characterized by stability and uniqueness.
Article
Materials Science, Multidisciplinary
A. Estyunin, E. F. Schwier, S. Kumar, K. Shimada, K. Kokh, O. E. Tereshchenko, A. M. Shikin
Summary: Contemporary studies of magnetic topological insulators require accurate measurements to investigate Dirac point gaps. In this study, the effect of band energy shift due to sample contamination and irradiation on electronic structure measurement using ARPES method is examined. The results show that the shifted topological surface state remains stable and can be used to store information, but it becomes significantly broadened and its intensity drops under irradiation.
Article
Multidisciplinary Sciences
Ruey-Lin Chern
Summary: This paper investigates the photonic topological phases in chiral metamaterials with diagonal chirality components. By introducing pseudospin states, the photonic system is described as two subsystems with spin-orbit Hamiltonians of spin 1, resulting in nonzero spin Chern numbers that determine the topological properties. Surface modes at the interface between vacuum and the chiral metamaterial are formulated by algebraic equations in the wave vector space. Specifically, the surface modes form a pair of spiral surface sheets wrapping around the Weyl cone, resembling the helicoid surface states in topological semimetals. At the Weyl frequency, the surface modes contain two Fermi arc-like states that concatenate to yield a straight line segment.
SCIENTIFIC REPORTS
(2023)
Article
Engineering, Mechanical
Lile Xie, Jie Cheng, Tongqing Wang, Xinchun Lu
Summary: By using atomic force microscopy and scanning electron microscopy, the study investigates the mechanical removal mechanism of silicon with different exposure surfaces of cerium oxide (CeO2). It is found that the main type of mechanical wear between Si and CeO2 is adhesive wear. The relationship between silicon removal rate, friction force, and ceria wear rate with different crystallographic orientations of CeO2 is also explored.
TRIBOLOGY INTERNATIONAL
(2021)
Article
Physics, Multidisciplinary
Xuming Qin, Yi Liu, Xiaowu Li, Gui Yang, Dongqiu Zhao, Lin Ju
Summary: Dirac materials with excellent electrical properties have attracted much attention in research, with the search and design of Dirac materials becoming a popular area of study. The mechanism for the formation of Dirac cones in two-dimensional materials with six-fold symmetry was analyzed and simple rules were proposed to determine the presence of Dirac cones in these materials.
NEW JOURNAL OF PHYSICS
(2021)
Article
Crystallography
Shashank Shekhar Mishra, Lu-Chung Chuang, Kensaku Maeda, Jun Nozawa, Haruhiko Morito, Kozo Fujiwara
Summary: This study investigates the growth rate of the crystal/melt interface along different crystallographic orientations. By comparing the growth rate on the {110} plane with that on other planes, it is observed that the growth rate on the {110} plane is faster. These differences may be attributed to the growth mode.
JOURNAL OF CRYSTAL GROWTH
(2022)
Article
Nanoscience & Nanotechnology
Asish K. Kundu, Genda Gu, Tonica Valla
Summary: Bismuth materials in Bi(110) films exhibit intriguing electronic structure properties, with the experimental verification of theoretical predictions providing insights for applications in quantum spin hall effects and beyond.
ACS APPLIED MATERIALS & INTERFACES
(2021)
Review
Nanoscience & Nanotechnology
S. Colonna, R. Flammini, F. Ronci
Summary: This paper reviews the research activity of the author's group in the field of silicene synthesis and properties, focusing on the interaction between silicon deposition and silicon substrate, and discussing the debated formation of silicene from unsaturated silicon compounds.
Article
Chemistry, Physical
Thomas Leoni, Conor Hogan, Kai Zhang, Michel Daher Mansour, Romain Bernard, Romain Parret, Andrea Resta, Stefano Colonna, Yves Borensztein, Fabio Ronci, Geoffroy Prevot, Laurence Masson
Summary: This study reports experimental and theoretical findings on the formation of dumbbell silicene structures on Ag(110), with STM observations perfectly reproduced by DFT calculations. The reconstructions are stabilized by ordered arrays of Si adatoms on top of silicene, confirming the growth of a dumbbell silicene layer. This research opens up possibilities for tuning the unique properties of silicene.
JOURNAL OF PHYSICAL CHEMISTRY C
(2021)
Review
Chemistry, Inorganic & Nuclear
Friedhelm Bechstedt, Paola Gori, Olivia Pulci
Summary: This review article focuses on the investigation of novel two-dimensional materials Xenes and their functionalized derivatives for potential applications in electronic and optoelectronic devices, discussing their atomic structure, band structure, absorption characteristics, and the influence of external conditions on electronic properties.
PROGRESS IN SOLID STATE CHEMISTRY
(2021)
Article
Materials Science, Multidisciplinary
Abderrezak Belabbes, Friedhelm Bechstedt, Silvana Botti
Summary: By conducting ab initio calculations, it has been demonstrated that perturbed hexagonal germanium is an excellent material for active optoelectronic devices in the infrared region. Perturbing the system through atomic substitution and applying strain can greatly enhance the oscillator strength and energy transition of the material, making it suitable for light emitting devices.
PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS
(2022)
Article
Chemistry, Physical
Fabio Ronci, Stefano Colonna, Roberto Flammini, Maurizio De Crescenzi, Manuela Scarselli, Matteo Salvato, Isabelle Berbezier, Holger Vach, Paola Castrucci
Summary: In this paper, an in-depth study was conducted on the growth of nickel silicides under different conditions. It was found that two different nickel silicides form progressively as the annealing temperature increases. The presence of a graphene layer does not alter the nature of the silicide phases but affects the morphology of the silicide overlayer.
APPLIED SURFACE SCIENCE
(2023)
Article
Materials Science, Multidisciplinary
Pedro Borlido, Friedhelm Bechstedt, Silvana Botti, Claudia Roedl
Summary: Ge-rich hexagonal SiGe alloys have emerged as new direct-gap semiconductors with potential for integration of photonics on silicon. Optical, transport, and thermoelectric properties of these alloys were investigated using first-principles methods. The alloy band gap remains direct below 45% Si content and optical spectra show tunability with composition. Transport coefficients exhibit similar behaviors in cubic and hexagonal alloys, but the latter display anisotropic response due to reduced symmetry. The Seffbeck coefficients and thermoelectric power factors show nonmonotonous variations with Si content regardless of temperature.
PHYSICAL REVIEW MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
Mousa Bejani, Olivia Pulci, Naser Karimi, Elena Cannuccia, Friedhelm Bechstedt
Summary: In this study, we conducted a detailed analysis of the electronic properties and lattice dynamics of different layers of beta-InSe through theoretical calculations. We found that the few-layers systems are indirect band gap semiconductors with a Mexican-hat-shaped top valence band. The phonon analysis revealed the dynamical stability of mono- and bi-layers, as well as the breakdown of the longitudinal-optical-transverse-optical splitting with an increase to four layers. The Raman and IR spectra were dominated by in-plane and out-of-plane lattice vibrations, and small shifts of the peak positions and variations of the peak intensities were observed as signatures of the number of layers.
PHYSICAL REVIEW MATERIALS
(2022)
Article
Chemistry, Physical
Giuseppe Mattioli, Giorgio Contini, Fabio Ronci, Roberto Flammini, Federico Frezza, Rosanna Larciprete, Venanzio Raglione, Paola Alippi, Francesco Filippone, Aldo Amore Bonapasta, Gloria Zanotti, Bertrand Kierren, Luc Moreau, Thomas Pierron, Yannick Fagot-Revurat, Stefano Colonna
Summary: In this study, we investigate the interface between (RuPc)2 and the Ag(001) surface. Two different commensurable arrangements of the molecules are observed at different coverage densities on the substrate. The focus of the study is on the evolution of interface states with molecular density and the charge distribution in the thin interfacial layer between molecules and substrate. The results reveal different valence band structures and charge modulations for the two molecular arrangements, making (RuPc)2/Ag(001) an interesting case of intermediate interaction between physisorption and chemisorption.
JOURNAL OF PHYSICAL CHEMISTRY C
(2023)
Article
Multidisciplinary Sciences
Giancarlo Cappellini, Juergen Furthmueller, Friedhelm Bechstedt, Silvana Botti
Summary: We conducted a systematic investigation on the electronic and optical properties of two crystals of alkaline earth metal fluorides using state-of-the-art techniques. The calculations were performed using density functional theory, many-body perturbation theory, and the Bethe-Salpeter equation. Our results showed distinctive properties for rutile MgF2 compared to cubic SrF2 and other members of the alkaline earth metal fluoride family. The excitonic effects in finite-sized systems were confirmed through a comparison between bulk and cluster calculations.
Article
Materials Science, Multidisciplinary
Martin Keller, Abderrezak Belabbes, Juergen Furthmueller, Friedhelm Bechstedt, Silvana Botti
Summary: In this paper, the energetic, structural, elastic, and electronic properties of hexagonal SiGe are analyzed using density functional theory. The phase diagram shows that the diamond structure is the most stable, but hexagonal modifications are close to the phase boundary. Band structure calculations predict significant changes in electronic states with hexagonality. Si is always a semiconductor with indirect band gaps, while the hexagonal Ge polytypes have direct band gaps. Band alignment based on the branch-point energy leads to type-I heterocrystalline interfaces between Ge polytypes.
PHYSICAL REVIEW MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Alessia Muroni, Simone Brozzesi, Friedhelm Bechstedt, Paola Gori, Olivia Pulci
Summary: We conducted a comprehensive study on the structural and electronic properties of a graphene/phosphorene heterostructure using density functional theory. We found that by optimizing the lattice constants, the in-plane strain of the heterostructure can be reduced to under 1%. The presence of weak van der Waals interaction between the graphene and phosphorene layers was confirmed. Additionally, we demonstrated that G/P heterostructures can form both n-type and p-type Schottky contacts under external perturbations, suggesting their potential for novel electronics applications and optoelectronic devices.
Article
Materials Science, Multidisciplinary
Abderrezak Belabbes, Silvana Botti, Friedhelm Bechstedt
Summary: This study investigates the natural and true band profiles at heterojunctions formed by hexagonal SixGe1-x alloys. The findings show that the natural band offsets are not significantly affected by different alignment methods or functional choices. Ge-rich alloys exhibit a type-I heterocharacter with direct band gaps, while Si-rich junctions are type-I but with an indirect band gap. The true band lineups at pseudomorphically grown heterostructures are strongly influenced by the biaxial strain generated in the adjacent alloys.
Article
Materials Science, Multidisciplinary
R. A. Zhachuk, D. Rogilo, A. S. Petrov, D. Sheglov, A. Latyshev, S. Colonna, F. Ronci
Summary: The atomic structure and dynamics of Sn adatoms on well-ordered single steps on the Si(111) - root 3 x root 3 - Sn surface were studied using low-temperature scanning tunneling microscopy (STM) and density-functional theory-based calculations. It was found that the Sn adatoms formed potential double wells near the steps, acting as traps and causing fluctuating current in these areas.
